1. Field of the Invention
This invention relates to a radiation image recording and read-out apparatus for recording a radiation image on a stimulable phosphor sheet, exposing the stimulable phosphor sheet to stimulating rays which cause the stimulable phosphor sheet to emit light in proportion to the stored radiation energy, detecting the emitted light to read out the radiation image, and converting the emitted light into electric signals. This invention particularly relates to a radiation image recording and read-out apparatus which is small and light, and in which the mechanism is simplified.
2. Description of the Prior Art
When certain kinds of phosphors are exposed to a radiation such as X-rays, .alpha.-rays, .beta.-rays, .gamma.-rays, cathode rays or ultraviolet rays, they store a part of the energy of the radiation. Then, when the phosphor which has been exposed to the radiation is exposed to stimulating rays such as visible light, light is emitted by the phosphor in proportion to the stored energy of the radiation. A phosphor exhibiting such properties is referred to as a stimulable phosphor.
As disclosed in U.S. Pat. No. 4,258,264 and Japanese Unexamined Patent Publication No. 56(1981)-11395, it has been proposed to use a stimulable phosphor in a radiation image recording and reproducing system. Specifically, a sheet provided with a layer of the stimulable phosphor (hereinafter referred to as a stimulable phosphor sheet) is first exposed to a radiation passing through an object such as the human body to have a radiation image of the object stored thereon, and is then two-dimensionally scanned by stimulating rays such as a laser beam which cause the stimulable phosphor sheet to emit light in proportion to the stored radiation energy. The light emitted by the stimulable phosphor sheet upon stimulation thereof is photoelectrically detected and converted to electric image signals by a photodetector, and the radiation image of the object is reproduced as a visible image by use of the image signals on a recording medium such as a photographic film, a display device such as a cathode ray tube (CRT), or the like.
In the aforesaid radiation image recording and reproducing system, the stimulable phosphor sheet is used to temporarily store the radiation image in order to reproduce the final visible image therefrom on a final recording medium. For economical reasons, therefore, it is desirable that the stimulable phosphor sheet be used repeatedly.
In order to reuse stimulable phosphor sheets as mentioned above, the radiation energy remaining on the stimulable phosphor sheet after it is scanned with stimulating rays to read out the radiation image stored thereon should be erased by exposure to light or heat as described in, for example, U.S. Pat. No. 4,400,619 or Japanese Unexamined Patent Publication No. 56(1981)-12599. The stimulable phosphor sheet should then be used again for radiation image recording.
From the aforesaid viewpoint, the applicant proposed in Japanese Unexamined Patent Publication No. 58(1983)-200269 a radiation image recording and read-out apparatus comprising, built in a single apparatus:
(i) a stimulable phosphor sheet capable of storing a radiation image thereon,
(ii) an image recording section for recording a radiation image of an object on the stimulable phosphor sheet by exposing the stimulable phosphor sheet to radiation passing through the object,
(iii) an image read-out section provided with a stimulating ray source for producing stimulating rays for scanning the stimulable phosphor sheet carrying the radiation image stored thereon at the image recording section, and a photoelectric read-out means for detecting light emitted by the stimulable phosphor sheet scanned with the stimulating rays to obtain electric image signals, and
(iv) an erasing section for, prior to the next image recording on the stimulable phosphor sheet for which the image read-out has been carried out at the image read-out section, having the stimulable phosphor sheet release the radiation energy remaining on the stimulable phosphor sheet,
whereby the stimulable phosphor sheet is used repeatedly for radiation image recording. With the proposed radiation image recording and read-out apparatus, the radiation image recording and read-out can be carried out sequentially and efficiently.
However, with the conventional radiation image recording and read-out apparatus, the stimulable phosphor sheet is conveyed for scanning with stimulating rays in the sub-scanning direction at the time of radiation image read-out, and therefore the apparatus is caused to become large and heavy and the mechanism is caused to become complicated by the conveyance mechanism for this purpose.
In order to eliminate the conveyance of the stimulable phosphor sheet, the applicant also proposed in Japanese Patent Application No. 62(1987)-21957 a radiation image recording and read-out apparatus wherein a stimulable phosphor sheet is maintained stationary, and a stimulating ray scanning system and a system for detecting light emitted by the stimulable phosphor sheet upon stimulation thereof are moved with respect to the stimulable phosphor sheet, thereby to carry out the radiation image read-out. However, with the proposed radiation image recording and read-out apparatus, though the stimulable phosphor sheet is maintained stationary, a mechanism for moving the stimulating ray scanning system and the system for detecting light emitted by the stimulable phosphor sheet is necessary. Therefore, even though the apparatus becomes small, a need exists for lightening of the apparatus and simplification of the mechanism.